Modern automobile design includes integration of various types of satellite service equipment, such as Global Positioning System (GPS) equipment, into vehicle hardware. Since GPS hardware characteristics, such as GPS receiver sensitivity and GPS antenna radiation patterns, vary across manufacturers and equipment models, the effect of new GPS hardware on GPS receiver performance is frequently tested via GPS signal simulators prior to acceptance of new equipment.
However, GPS signal simulators, such as those manufactured by Spirent, predict the effect of emulated GPS signals and GPS satellite constellations by connecting a physical (i.e., hardware) GPS test receiver to the signal emulator, thereby increasing cost and reducing versatility. Furthermore, GPS signal performance depends heavily on a specific GPS antenna in use and on the type of vehicle operating environment. For example, a specific antenna radiation pattern, as well as the type, height and location of buildings, trees, and other factors affecting propagation conditions in a particular locale, impact GPS receiver performance. Hardware based GPS simulators require a user to specify a straight drive route with specific buildings of certain heights and attenuation attributes in an attempt to take into account a user-specific operating environment. However, this method of including environmental effects into a simulation scenario is very time consuming, only covers limited user specific scenarios, and does not take into account changes in GPS antenna gain with respect to a given satellite in view due to sharp vehicle turns. Hence, hardware based simulators may require the user to manually create hundreds or thousands of different simulation scenarios to cover drive routes and local environment effects to account for many possible GPS signal propagation conditions in a typical vehicle operating environment (e.g., open sky, urban, suburban, etc). Another way of taking into account environmental effects includes field data collection campaigns where GPS signal data is collected from an actual vehicle traveling along a specified drive route to model a typical vehicle operating environment and/or effects of a given GPS antenna. However, such measurement campaigns are both equipment and labor intensive. Furthermore, field measurement data from one city may not equally apply to predicting GPS receiver performance in another city with different environmental factors, such as different foliage and building types.
Therefore, a need exists for a software based GPS system simulator that predicts the effect of various GPS hardware characteristics, such as specific GPS antenna patterns, without requiring a connection to GPS hardware or field measurement campaigns to take into account a wide variety of vehicle operating environments.